Hide your pot! Here comes the Nasal Ranger

Ben Siller of Denver environmental health, uses the Nasal Ranger, a device that helps officials detect the intensity of an odor by filtering out the odorous air. (Hyoung Chang/The Denver Post)

Ben Siller looked ridiculous on a recent afternoon, standing on a downtown Denver, Colo., street corner with a giant device clamped to his face sniffing the air for odorous evidence of marijuana.

“What are you doing?” asked Jimmy Smith, owner of Higher Expectations dispensary south of Mississippi Avenue near the South Platte River.

In the dawning age of legal marijuana in Denver, the city is getting more and more complaints about the unmistakable odor wafting through the streets — a skunky, herbal scent that has prompted dozens of calls to the city's hotline.

That's when Siller with his Nasal Ranger device jumps into action.

An investigator with the Denver Department of Environmental Health, Siller for 26 years has been looking into odor complaints. They can range from smoke from a kitchen to industrial odors.

Siller will bring his device to the area and sniff the air, determining whether the odor violates the city odor law. Rarely does that happen.

“It has to be a very strong odor,” Siller said.

The pungent odor of marijuana plants or even second-hand pot smoke won't violate the odor law, which is determined by volume. A violation occurs after the odor exceeds the 7-1 ratio — when one volume of odor is detectable with seven or more volumes of nonodorous air.

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The Nasal Ranger — the conelike contraption that Siller attaches to his nose — dials in the strength of the odor. Almost never does the smell surpass the 7-to-1 dilution threshold.

It hasn't happened since 1994. Odors would have to be pretty strong, an industrial-level aroma, like what would come from an ill-managed rendering plant.

Marijuana smoking or grow facilities won't reach that level, Siller said. Most grow facilities have ventilation systems and filters to prevent odors from escaping, even when marijuana cultivation is at its stinkiest during the harvest times, said Smith, owner of Higher Expectations.

Siller also advises warehouses to be good neighbors and try to reduce the odors as best they can, even though they are not breaking the law.

The city also may issue citations when five or more residents call in an odor complaint within a 12-hour period. That also rarely happens but is more frequent.